Gang-control condenser



July 2, 1929. E. s. DANIELSON GANG CONTROL CONDENSER Filed Nov. 9, 1926 2 Sheets-Sheet a E I F this kind however have been Patented July 2, 1929.

UNITED STATES ERNEST G. DANIELSON, OF FRANCISCO, CALIFORNIA.

GANG-CONTROL CONDENSER.

Application filed November 9, 1926. Serial No. 147,370.

This invention relates generally to devices for simultaneously tuning a plurality of electrical circuits.

In radio apparatus such as broadcast receivers, it is common practice to use gang control condensers for the purpose of tuning the various resonant circuits employed. For example, in radio apparatus utilizing cascade radio frequency amplifiers, the successive stages are tuned by variable condensers which are operated from a common control. Such arrangement will function properly provided the electrical properties of the circuit and that of the variable condensers are identical. In practice however the circuits of a receiving set are not identical and manufactured condensers vary somewhat-as to characteristics. To obviate this difficulty it has been proposed to employ suitable means such as a cam mechanism associated with the gang control whereby the individual condensers are automatically given a movement which will maintain the different circuits in resonance throughout the movement of the control. Prior devices of impractical from a mechanical standpoint and have not been well adapted for incorporation with the present day broadcast receivers.

It is an object of this invention to devise a practical gang control condenser assembly which will incorporate cam means for automa-tically securing proper movement of the individual condensers.

It is a further object of this invention to incorporate a straight line frequency variable condenser in combination with a straight line frequency Vernier.

Further objects of this invention will appearfrom the following description in which I have set forth the preferred embodiment of my invention. It is to be understood that the invention is to be accorded a range of electrical and mechanical equivalents consistent with the state of the prior art.

Referring to the drawings:

Figure lis a plan view of a gang control condenser assembly incorporating the principles of this invention.

Figure 2 is a side elevational view of the assembly shown in Fig. l.

Figure 3 is a cross sectional view taken along the line 33 of Fi 1. V

Figure 4 is a detail viewillustrating the manner of determining the shape of the compensating cam.

The invention consists generally in incorporating a particular form of cam compensating mechanism with a gang control condenser assembly. The individual condensers of the assembly are preferably of the type which employ a pair of relatively movable electrodes and the cam mechanism is associated with the gang control in such a manner that it automatically serves to bodily shift the electrodes of an individual condenser to secure a compensating Vernier adjustment. It is also proposed to utilize straight line frequency condensers and to construct the compensating mechanism in such a manner that it will have a similar characteristic.

The particular embodiment of the invention which I have illustrated in thedrawings comprises a plurality of variable condensers 11, 12 and 13. The condenser 11 for example serves to tune the antenna circuit of a radio receiving set, the condenser 12 may tune the coupling between the first and second radio frequency amplifier stages, and condenser 13 the coupli g between the second amplifier stage and a detector or modulator. For convenience in incorporating the assembly with a radio receiving set these condensers have been shown as mounted upon a suitable support panel 14 which also serves as a convenient support for the gang control mechanism. While any particular arrangement may be employed to suit requirements of in-, dividual radio apparatus, in this instance the support panel 14 has been shown as exteiiding at right angles to the instrument panel 16 of a radio set and the gang control is actuated by means of a graduated dial 17 or other suitable manual control.

The individual condensers which are employed are preferably of the type employing a pair of electrodes which are with respect to their supporting base. Thus the condensers illustrated comprise a pair of electrodes 18, each rotatably mounted upon'a suitable base member 19. These electrodes are of usual construction,- comprising a plurality of spaced plates of conductive material disposed in such a manner that the plates of one electrode are adapted to interleave the plates of the other electrode, thereby establishing an electrical capacitance. Such a condenser has been shown and claimed in the copending application of Wise and Danielson No. 728,480. entitled Variable condenser. F or securing relative movement of the electrodes there is provided a rotatable control shaft 21 which projects through the support panel 14.

The mechanism for interconnecting the shaft 21 with the electrodes 18 is preferably such that the condensers will have a straight line frequency characteristic, that is, angular movement of the shaft 21 within the capacitance range of the condenser will have a linear function with respect to the frequency of the condenser when employed with a standard inductance. This mechanism for example may be of the kind described in my copending application No. 111,193, entitled Variable condenser. Mechanism of this kind is shown in detail in Fig. 3 and comprises briefly a pair of intermeshing gears 23,

each 'fixed with respect to one of the condenser electrodes 18 so as to cause the same to rotate simultaneously in opposite directions. Rotary movement is imparted to one of the gears by means of a'cam 24 which is fixed to I the shaft 21 and which serves to oscillate a .densers. The particular grooved periphery lever 25. One end of lever is pivotally mounted to the base 19 is by the pivot pin 26, and the other end is pivotally secured to one of the gears 23 by means of pin 27. Cam 24 is in the form of a spiral groove or slot 28 engaging a pin 29 projecting from the lever 25, the cam slot 28 being cut in such a manner as to impart a relative movement to the electrode which is disproportionateto the angular movement of the shaft 21. In this particular case this movement is proper to impart to the condenser the desired straight line frequency characteristic. In order to be able to adjust the minimum capacitance of the individual condensers, the pin 27 is adjustably disposed within a slot 30 provided in the gear 23 and also engages a slot 31 in the end of lever 25. Slot 30 however is inclined at an I angle to the radii of gear 23 while slot 31 is substantially in alignment with pivot pin 26. Therefore by adjustlng the position of pin 27 as by means of a set screw 32 the minimum capacitance of the condenser may be adjusted without making any change in the maximum capacitance. When the cam 24 has been rotated to move the electrodes in their maximum capacitance position the slots 30 and 31 are substantially in alinement so that adjustment of-pivot pin 27 has no effect upon this setting.

Any suitable means may be employed for effecting unison control of the individual conmechanism employed comprises a pulley 33 fixed to each condenser shaft 21 and provided with a 34. Wound about these pulleys there is resilient wire 35, the ends of this wire being connected to and tensioned by means of a spring 36 disposed within a recess 37 provided upon the face of one of the pulley wheels 33. The control dial 17 is preferably mounted upon a rotatable control shaft 38 which is mechanically connected to one of the pulley wheels 33 as by means of bevel gears 39.

The compensating means for securing automatic individual adjustment of the condensers 11 and 12- preferably comprises in each instance a cam disc 40 which is detachably secured to the pulley wheel 33 as by means of a screw 41 and a pin 42 projecting from the face of the pulley wheel in an aperture in the disc. Adapted to engage the curved periphery 43 of.this cam 40 there is an arm 44 pivotally mounted to the support panel 14 as by means of pin 45. This arm 44 is connected by means of a system of levers and links to the base 19 of the condenser in such a manner as to bodily rotate this base about the control shaft 21, thus bodily shifting the electrodes 18 with respect to the support panel 14. Thus there is provided a lever 51 fixed with respect to arm 44, lever 51 being connected to another lever 46 as by means of links 47. Lever 46 is fixed with respect to a plate 48 which in turn is fixed with respect to the base member 19 as by means of bolts 49. These bolts preferably extend through arcuate slots 50 in the support panel 14 whereby oscillatory movement imparted to lever 46 serves to rotate the base member 19 between certain limits. Rotation of the base member 19 with respect to the shaft 21 serves to provide a vernier adjustment between the electrodes 18 since such movement will cause movement of the pin 29 in the cam slot 28. As this vernier movement is secured through the cam 24 it will also have a straight line frequency characteristic the same as when the condenser is varied by direct rotation of shaft 21. The arm '44 is normally biased into contact with the cam face 43 as by means of a tensioning spring 52 interconnecting the levers 51 and 46.

As the electrical characteristics of the different electrical circuits will vary with dif ferent radio sets and with a change in the particular antenna employed, I have provided means to enable an operator to determine the shape of the cams 40 after the condenser assembly has been connected with the radio circuit. Thus the arm 44 has been shown as provided with a small roller 54 detachably mounted between the resilient extremities 55 and 56. The extremity 56 is also provided with a small aperture 57 for receiving the end of a suitable marking tool. This aperture 57 is located so that its center will coincide with the periphery of the roller 54. Manual control of the arms 44 is secured by means of the knobs 58 rotatably mounted upon the support panel 14 provided with cams 59 adapted to engage the levers 51. As an alternative means in place of the knobs 58 there may be provided adjusting screws 60 which may be screwed up against the levers 51.

In order to determine the shapes of the cams 40 for a particular radio apparatus the condensers 11 and 12 are adjusted by rota- 'tion of knobs 58 or by turning set screws 60 until they are in resonance with a station adjacent one limit of the wave length range to which the condenser 13 is tuned. A marking 7 tool is then inserted in the aperture 57 and suitable marks placed upon the face of blank cam discs which have been previously attached to the faces of pulley wheels 33. This process is repeated for a plurality of wave lengths spaced over the broadcast range until a sufficient number of points 62 are secured to determine the contour of'the cam. The blank discs are then removed and cut along the curve determined by these points. These cams when again secured to the pulley wheels 33 will automatically adjust the condensers 11 and 21 so as to bring all of the circuits in correct resonance. By utilizing a straight line freq-uency vernier the curvature of the cams is made more uniform so that in practice it 'is possible for a manufacturer to market a gang control assembly of this kind together with say three or four cams of slightly different curvature. By a slight amount of experimentation the user may then determine the correct cam to suit his particular type of receiving apparatus.

I claim:

1. In a. device of the class described, a plurality of variable tuning units, a gang control for said units, means for bodily shifting one of said units to secure individual variation of its tuning effect and means associated with said gang controlfor automatically controlling said means according to the setting of the gang control.

2. In' a device of the class described, a plurality of variable tuning units, a gang control for said units, means for bodily shifting one of said units to secure indivi ual variation of its tuning effect and cam means for automatically controlling said means according to the setting of the gang control.

3. In a device of the class described, a plu rality of variable tuning units each comprising a pair of movable elements, a gang control for said units, means for bodily shifting one of said units to secure individual adjustment of its elements, and means associated with said gang control for automatically controlling said means according to the setting of the gang control.

4. In a device of the class described, a pair of variable tuning units, each unit comprising a pair of elements secured to a common mountlng and a rotatable shaft for moving both of said elements relative to themountengagement with the cam surface of the disc,

said arm being adapted to receive a marking tool coincident With the periphery of the roller.

6. In a device of the class described, a support panel, a plurality of variable tuning units secured to said panel, each unit including a rotatable shaft, a gang control for said units, a cam secured to the shaft of at least one of said units, and mechanisms controlled by said cam and mounted on said panel for securing compensating movement of the elements of said one unit.

7 In a tuning device of the class described, a pair of electrical elements pivotally secured to a common mounting, whereby they ma rotate about spaced arallel axes, means inc uding a rotatable sha t disalined with respect to said axes for moving both of said elements relative to the mounting, and, cam means operable automatically upon rotation of said shaft for effecting small compensating movements of said electrodes.

8. In a tuning device of the class \described, a pair of electrical elements pivotally secured to a common mounting whereby they may rotate about spaced parallel axes, means including a rotatable shaft disalined with respect to said axes for moving both of said elements relative to the mounting, and means operable automatically upon rotation of said shaft for effecting small compensating movements of said electrodes.

9. In a tuning device, ber, supported by said member, control means for effecting major movements of both of said elements relative to each other and relative to said supporting member, and means for effecting automatic com ensating relative movements of said electro es upon operating said control means.

In testimony whereof, I have hereunto set my hand.

ERNEST G. DANIELSON.

a supporting mema pair of electrical elementsmovably 

